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<h1>

  React v0.5

</h1>

<p class="meta">
  October 16, 2013
  by
  
    
      <a href="https://twitter.com/zpao">Paul O’Shannessy</a>
    
    
  
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  <p>This release is the result of several months of hard work from members of the team and the community. While there are no groundbreaking changes in core, we&#39;ve worked hard to improve performance and memory usage. We&#39;ve also worked hard to make sure we are being consistent in our usage of DOM properties.</p>

<p>The biggest change you&#39;ll notice as a developer is that we no longer support <code>class</code> in JSX as a way to provide CSS classes. Since this prop was being converted to <code>className</code> at the transform step, it caused some confusion when trying to access it in composite components. As a result we decided to make our DOM properties mirror their counterparts in the JS DOM API. There are <a href="https://github.com/facebook/react/blob/master/src/dom/DefaultDOMPropertyConfig.js#L156">a few exceptions</a> where we deviate slightly in an attempt to be consistent internally.</p>

<p>The other major change in v0.5 is that we&#39;ve added an additional build - <code>react-with-addons</code> - which adds support for some extras that we&#39;ve been working on including animations and two-way binding. <a href="/react/docs/addons.html">Read more about these addons in the docs</a>.</p>

<h2>Thanks to Our Community</h2>

<p>We added <em>22 new people</em> to the list of authors since we launched React v0.4.1 nearly 3 months ago. With a total of 48 names in our <code>AUTHORS</code> file, that means we&#39;ve nearly doubled the number of contributors in that time period. We&#39;ve seen the number of people contributing to discussion on IRC, mailing lists, Stack Overflow, and GitHub continue rising. We&#39;ve also had people tell us about talks they&#39;ve given in their local community about React.</p>

<p>It&#39;s been awesome to see the things that people are building with React, and we can&#39;t wait to see what you come up with next!</p>

<h2>Changelog</h2>

<h3>React</h3>

<ul>
<li>Memory usage improvements - reduced allocations in core which will help with GC pauses</li>
<li>Performance improvements - in addition to speeding things up, we made some tweaks to stay out of slow path code in V8 and Nitro.</li>
<li>Standardized prop -&gt; DOM attribute process. This previously resulting in additional type checking and overhead as well as confusing cases for users. Now we will always convert your value to a string before inserting it into the DOM.</li>
<li>Support for Selection events.</li>
<li>Support for <a href="https://developer.mozilla.org/en-US/docs/Web/API/CompositionEvent">Composition events</a>.</li>
<li>Support for additional DOM properties (<code>charSet</code>, <code>content</code>, <code>form</code>, <code>httpEquiv</code>, <code>rowSpan</code>, <code>autoCapitalize</code>).</li>
<li>Support for additional SVG properties (<code>rx</code>, <code>ry</code>).</li>
<li>Support for using <code>getInitialState</code> and <code>getDefaultProps</code> in mixins.</li>
<li>Support mounting into iframes.</li>
<li>Bug fixes for controlled form components.</li>
<li>Bug fixes for SVG element creation.</li>
<li>Added <code>React.version</code>.</li>
<li>Added <code>React.isValidClass</code> - Used to determine if a value is a valid component constructor.</li>
<li>Removed <code>React.autoBind</code> - This was deprecated in v0.4 and now properly removed.</li>
<li>Renamed  <code>React.unmountAndReleaseReactRootNode</code> to <code>React.unmountComponentAtNode</code>.</li>
<li>Began laying down work for refined performance analysis.</li>
<li>Better support for server-side rendering - <a href="https://github.com/facebook/react-page">react-page</a> has helped improve the stability for server-side rendering.</li>
<li>Made it possible to use React in environments enforcing a strict <a href="https://developer.mozilla.org/en-US/docs/Security/CSP/Introducing_Content_Security_Policy">Content Security Policy</a>. This also makes it possible to use React to build Chrome extensions.</li>
</ul>

<h3>React with Addons (New!)</h3>

<ul>
<li>Introduced a separate build with several &quot;addons&quot; which we think can help improve the React experience. We plan to deprecate this in the long-term, instead shipping each as standalone pieces. <a href="/react/docs/addons.html">Read more in the docs</a>.</li>
</ul>

<h3>JSX</h3>

<ul>
<li>No longer transform <code>class</code> to <code>className</code> as part of the transform! This is a breaking change - if you were using <code>class</code>, you <em>must</em> change this to <code>className</code> or your components will be visually broken.</li>
<li>Added warnings to the in-browser transformer to make it clear it is not intended for production use.</li>
<li>Improved compatibility for Windows</li>
<li>Improved support for maintaining line numbers when transforming.</li>
</ul>

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